Our method for the large scale fractionation of Drosophila egg chambers makes it possible to study biochemical events during Drosophila oogenesis. The availability of this method makes Drosophila a choice organism for the study of oogenesis in general and for the study of how the egg prepares itself for the extremely fast events of early embryogenesis. The following aspects shall be examined: a) Study the regulation of transcription and translation of the genes coding for histones and actin. These proteins and the corresponding mRNAs shall be quantitated in egg chambers of different developmental stages and in unfertilized eggs. Storage of histones will be compared in eggs of Drosophila, sea urchin and surf clam. We shall also distinguish between mRNAs associated with post-ribosomal ribonucleoprotein particles (stored mRNA) and with polysomes (active mRNA). Spacial distribution of RNA sequences in the growing egg chamber shall also be examined. Results should provide extensive information on the dynamics of synthesis and storage of specific gene products. b) A few exceptional mRNA's ("oocyte mRNA's) were shown to be excluded from the polysome compartment in Drosphila unfertilized eggs and appear to be under specific translational control. We shall clone DNA sequences complementary to "oocyte mRNA's" and probe for the expression of the corresponding genes during oogenesis, early embryogenesis and other developmental stages. With these studies we expect to characterize sequences which play a specific role in oogenesis/and/or early development of Drosophila. It is hoped that the understanding of oogenesis at a biochemical level will provide some insights into the obvious link between the egg and the embryo.